Multi-stage voltage dependent load modelling of fast charging electric vehicle

2021

Energies

The increasing share of distributed energy resources aggravates voltage limit compliance within the electric power system. Nowadays, various inverter-based Volt/var control strategies, such as cosφ(P) and Q(U), for low voltage feeder connected L(U) local control and on-load tap changers in distribution substations are investigated to mitigate the voltage limit violations caused by the extensive integration of rooftop photovoltaics. This study extends the L(U) control strategy to X(U) to also cover the case of a significant load increase, e.g., related to e-mobility. Control ensembles, including the reactive power autarky of customer plants, are also considered. All Volt/var control strategies are compared by conducting load flow calculations in a test distribution grid. For the first time, they are embedded into the LINK-based Volt/var chain scheme to provide a holistic view of their behavior and to facilitate systematic analysis. Their effect is assessed by calculating the voltage limit distortion and reactive power flows at different Link-Grid boundaries, the corresponding active power losses, and the distribution transformer loadings. The results show that the control ensemble X(U) local control combined with reactive power self-sufficient customer plants performs better than the cosφ(P) and Q(U) local control strategies and the on-load tap changers in distribution substations.

Section: Customer Plant Levelmentioning

confidence: 99%

“…The St.-model represents the EV batteries that are connected to the CP_Link-Grid through three EV chargers. Their P-behavior is determined by ZIP-coefficients [40] and load profiles [41] (Figure A1c). No reactive power is absorbed or injected.…”

Section: Conflicts Of Interestmentioning

confidence: 99%

Effect of Individual Volt/var Control Strategies in LINK-Based Smart Grids with a High Photovoltaic Share

2021

Energies

“…Its reactive power contribution is set to zero. -model, the active power absorbed by the charger is specified using ZIP models from [27] and load profiles from [28], see Equation (3a) and Figure 7d. Its reactive power contribution is set to zero.…”

Section: Structurementioning

confidence: 99%

“…The St.-model represents an EV battery that is connected to the CP through the EV charger. By analogy with the Dev.-model, the active power absorbed by the charger is specified using ZIP models from[27] and load profiles from[28], see Equation (3a) and Figure7d. Its reactive power contribution is set to zero.P CP−St…”

mentioning

confidence: 99%

Increasing the Utilization of Existing Infrastructures by Using the Newly Introduced Boundary Voltage Limits

2021

Energies

The increasing share of distributed generation aggravates voltage limit compliance at customers’ delivery points. Currently, grid operators validate compliance with the voltage limits specified in Grid Codes by conducting load flow simulations at the medium voltage level, considering the connected low voltage grids as ‘loads’ to reduce the modeling effort. This approach does not support the accurate validation of limit compliance, as the voltage drops at the low voltage level are unknown. Nevertheless, to guarantee acceptable voltages even under worst-case conditions, safety margins are involved that impair the utilization of the electricity infrastructure. This study conducts load flows simulations in a test distribution grid, revealing the variable character of the voltage limits at different system boundaries. The conventional load model is extended by new parameters—the boundary voltage limits—to enable the consideration of variable voltage limits in load flow analysis of LINK-based smart grids. The standardized structure of the LINK-architecture allows for the systematic and accurate validation of voltage limit compliance by reducing the required modeling data to the technically necessary minimum. Use cases are specified that allows smart grids to increase the utilization of the electricity infrastructure by day-ahead scheduling and short-term adaptation of boundary voltage limits.

“…The St.-model represents the battery of the EV that is connected through the EV charger. By analogy with the Dev.-model, the active power absorbed by the charger is specified using ZIP models from [64] and load profiles from [6], Eq. (4.43).…”

Section: Storage Modelmentioning

confidence: 99%

Volt/var Chain Process*

A Holistic Solution for Smart Grids Based on LINK– Paradigm

2021

Simplicity is the ultimate sophistication.-Leonardo da Vinci IntroductionPhysically, the voltage is a local quantity that differs in each node of the electricity grid, as it varies along with the power transfer and the characteristics of the grid. Due to their strong coupling, the reactive power has always been used to control the voltage in transmission grids, originating the term Volt/varprocess. Reactive power is produced and consumed by diverse appliances distributed throughout the power system and operated by different stakeholders, making Volt/var control an extremely complex issue by its very nature. The overall control strategy should be designed with special care to reduce the complexity of the resulting Volt/var chain to facilitate the management.Volt/var management is one of the most fundamental power system processes that enables the reliable and efficient operation of the electricity grids. It is used to ensure compliance to voltage limits and to keep the power factor close to one. Both the elimination of voltage limit violations and the minimisation of the reactive power flows extend the active power transfer capability of the grid. In other words, an appropriate Volt/var control increases the utilisation of the electrical infrastructure, thus lowering the need for grid reinforcement.The massive connection of renewable and distributed generation and the electrification of other sectors gave rise to new challenges and opportunities that call for an adaption of the traditional Volt/var control schemes. Deteriorated power quality and uncontrolled interactions between the systems operated by different stakeholders are recognised as the main problems to be solved by future smart grids [66]. Meanwhile, the ability of distributed energy resources to participate in the Volt/var process